Hsp110 and Hsp70 mediate luciferase refolding in an Hsp40-dependent manner. (A) Luciferase refolding after preincubation with Hsc70. Firefly luciferase was heat-denatured at 42°C in the presence of Hsc70. Refolding was performed at 30°C in the presence of either Hsp110, Hsp40, or both, and ATP. In total, 100% activity corresponds to the enzyme activity of native luciferase in refolding buffer. (B) Luciferase refolding after preincubation with Hsp110 or Hsc70. Here, luciferase was denatured at 42°C in presence of Hsp110 or Hsc70 and folded at 30°C by adding ATP and different combinations of Hsc70, Hsp110, and Hsp40. Folding yields were similar irrespective of the order of Hsc70 and Hsp110 addition, indicating that the prevention of aggregation activity of Hsp110 is not a critical determinant for efficient protein refolding by the Hsp70–Hsp110 system. (C) Luciferase refolding by Ssa1p, Sse1p, and Ydj1p (yeast Hsp70/Hsp110/Hsp40). Luciferase was denatured in the presence of Ssa1p as described in (A). (D) Refolding of chemically denatured luciferase by Hsp70/Hsp110/Hsp40. (E) Hsp110 concentration dependence of luciferase refolding by the Hsp70/Hsp110/Hsp40 system. The concentrations of all other components were unchanged.